Secretions from the apocrine sweat glands, which are primarily located in the human underarm, are largely odorless. The human underarm is consistently warm, and sweat glands present in the underarm provide moisture, which when excreted, has a vital cooling effect. When adult underarms are washed with alkaline pH soap, the skin loses its acid mantle (pH 4.5-6), raising the skin pH and disrupting the skin barrier. Many bacteria thrive at this elevated pH, making the skin susceptible to bacterial colonization. The bacteria feed on the secretions from the apocrine glands, and on dead skin and hair cells, which results in the degradation of long-chain fatty acids into shorter chain acids such as formic acid or butyric acid, which are the primary cause of body odor.
Deodorants function in many ways to eliminate odor. For example, they are able to mask or complement the odor to minimize the offensive smell; trap the odor so that the volatile components do not reach the nose; or prevent or slow down the generation of volatile odiferous chemicals. Deodorants can also be formulated with antimicrobials to slow bacterial growth. For such formulations to be effective, antimicrobials should be easily applied and remain active on the skin for many hours. Inhibitors of perspiration (antiperspirants), which directly influence the secretion of perspiration, are also used to eliminate body odor. For easy application, antimicrobials need to be compatible with typical deodorant ingredients and, for consumer acceptance should not have adverse effects on skin. Additionally, deodorants should be developed so as to not react with sweat or create yellow stains on clothing.
Octenidine, in particular octenidine dihydrochloride, is an antimicrobial agent which has been previously described for use in antiseptic agents for the skin, the mucous membranes and wound antisepsis. Octenidine is known to strongly adhere to lipid components in cell membranes, which contributes to its high antimicrobial effect while at the same time being well tolerated by the human epithelia and traumatic tissues. Octenidine primarily acts anti-bacterially due to its affinity to bacterial surfaces. Consequently, the inclusion of octenidine, in particular octenidine dihydrochloride, in antiseptic preparations has been effective against microorganisms which contribute to, for example, body odor, blemished and/or oily skin, comedones, dandruff and foot odor.
Additionally, octenidine dihydrochloride has a disinfecting/antimicrobial effect against fungi and viruses. Consequently, the inclusion of octenidine hydrochloride in preparations for use in wound cleaning and as a disinfectant in treating hard surfaces such as, for example, operating room tables and laboratory equipment has also been previously described.
Octenidine and octenidine dihydrochloride are described in U.S. Pat. Nos. 4,206,215 and 4,442,124 as antimicrobial preparations and in U.S. Publication No. US2011/0217360 for wound and mucous membrane antisepsis, each of which is hereby incorporated by reference.
Although the benefits of octenidine are well documented, it has recently emerged that, as described in U.S. Publication No. US2011/0003857, antimicrobial octenidine compositions, such as octenidine dihydrochloride, have a tendency towards decomposition upon prolonged storage, for example, a period of several months. It is also established that degradation products can form from octenidine dihydrochloride alone and when used in combination with certain auxiliaries, which causes peroxides and aldehydes to form. Moreover, when antimicrobial octenidine dihydrochloride compositions are used in aerosol containers made of, for example, tinplate, aluminum, stainless steel, and other metals, the octenidine composition has caused corrosion in the aerosol container.
Thus, there is a need for antimicrobial compositions that facilitate easy application on the skin, do not penetrate the skin, are compatible with typical deodorant and cosmetic ingredients, and do not cause adverse effects (e.g., irritation) to skin and clothing. Additionally, there is also a need for antimicrobial compositions for use in wound cleaning and as a biocide for treating hard surfaces. Moreover, there is a need for antimicrobial compositions that are stable when stored at a comparatively high concentration, even at elevated temperatures, without degradation, formation of decomposition products or reduction in active ingredient content and do not cause corrosion of the dispenser.